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News release , National Institutes of Health _ February 4, 2010

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For Immediate Release

Thursday, February 4, 2010

Contact:

Wenger

(301) 496-7243 (NIDCD office)

(240) 398-1196 (during meeting)

Media Advisory

Effectiveness of a Second Cochlear Implant, New Life for Damaged Hair Cells

Among Topics to be Featured at International Conference of Ear, Nose, and

Throat Researchers

What: Scientists supported by the National Institute on Deafness and

Other Communication Disorders (NIDCD), one of the National Institutes of

Health, will be presenting their latest research findings at the 2010

Midwinter Meeting of the Association for Research in Otolaryngology (ARO).

When: February 6-10, 2010

Where: The Disneyland Hotel, Anaheim, Calif.

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Additional Information: Research topics to be presented by NIDCD-funded

scientists will include:

Noise-Damaged Hair Cells Can Regrow Stereocilia in Mammals if Rescued in

Time

Scientists have been trying to regenerate hair cells — sensory cells in the

inner ear named for the hairlike bundles jutting from their tops — out of

surrounding non-sensory cells as a way to make up for hair cell loss in ears

damaged by noise, some medicines, and other sources. (Unlike other

vertebrates, mammals aren’t able to grow new hair cells on their own once

the cells are dead or damaged.) But new NIDCD-funded research from Creighton

University, Nebraska, and the Chinese PLA General Hospital, Beijing, says

that hair cells damaged by noise may have more life in them than we once

thought. We may be able to regenerate new hair bundles — called

stereocilia — from the original hair cells. The researchers subjected guinea

pigs to an impulse noise simulating gunfire, resulting in severe hearing

loss. Using scanning electron microscopy, they showed extensive stereocilia

damage had occurred throughout the inner ear. However, when the researchers

injected math1, a key gene for the development of hair cells, into the inner

ear within one week of damage, they found that the stereocilia were able to

grow back. Furthermore, key measurements showed that the new stereocilia

were able to convert sound vibrations into electrical signals, which is how

the brain interprets sound. The researchers caution that there is a window

of time when the hair cells are still viable following noise damage. If the

hair cells are not rescued within that time frame, they will die. But if

researchers are able to intervene early enough — within 10 days — the hair

cells can possibly be saved. The researchers plan to conduct tissue culture

studies to confirm whether these findings are supported at the cellular

level.

The talk " Regeneration of Stereocilia of Cochlear Hair Cells by Math1 Gene

Therapy " (#484) takes place Sunday, Feb. 7, at 5:00 p.m. PT in the

Disneyland South Ballroom.

Success of Second Cochlear Implant Depends on Age at Which Child Receives

First Implant

The cochlear implant has been a highly successful biomedical technology for

the treatment of severe to profound hearing loss in children. Parents of

children who wear a cochlear implant face the question of whether two

implants would be better than one. However, the success rate of the second

implant has varied across studies, and researchers haven’t understood why.

In new NIDCD-funded research from the University of Colorado at Boulder,

Arizona State University, and the Rocky Mountain Ear Center, scientists have

found that the age at which a child receives his or her first implant is

extremely important in determining whether the second implant will be

effective. They studied 38 children, all of whom received their first

cochlear implant by 3½ years of age, and who received their second implant

between the ages of 1 and 17 years. Measuring neural activity in the

auditory cortex, the hearing center of the brain, the researchers found that

children who received their first implant under age 1½ years responded well

to the second implant, even if they received the second implant as late as 9

years of age. Conversely, virtually all children who received their first

implant at 2½ years or later did not respond as well to the later second

implant, regardless of when they received it. These results were backed up

by studies of how well the participants understood speech in both quiet and

noisy conditions. The researchers plan to investigate a possible mechanism

underlying their findings by incorporating brain imaging technology to

determine if early implantation stimulates both sides of the brain, while

later implantation activates only one side.

The poster “A Sensitive Period for Cortical Development and Plasticity in

Children with Sequential Bilateral Cochlear Implants” (#897) takes place

Monday, Feb. 8, at 1:00 p.m. PT in the Disneyland Exhibit Hall.

A Dinner Party Dilemma: How Does Your Brain Sift through the Sounds of Too

Many Talkers?

If you’re trying to follow one dinner party conversation amid a lot of

background chatter, your brain cells are doing the same thing.

NIDCD-supported researchers have found that when you are in an environment

where there are many competing sounds, nerve cells in the auditory cortex —

the part of the brain that interprets the sounds you hear — divide up the

listening duties so that one population of neurons will focus on one sound

source and another population will focus on the second source. In research

conducted by the University of California, Irvine, University of Michigan,

and University of Western Ontario, study participants who were surrounded by

loudspeakers were asked to identify a rhythmic pattern played from one sound

source when it was played at the same time as a competing pattern. Not

surprisingly, they found that the participants had a tough time telling the

patterns apart when they came from the same speaker. But when the sources of

the sounds were spaced a very small distance apart from each other — as

little as 5-10 degrees — they had no problem identifying the sound patterns.

In addition, in a similar study with cats, the researchers recorded neural

activity in the auditory cortex when competing sounds were played. They

found that when the sounds came from the same speaker, auditory neurons were

synchronized to the combined sounds, but when the sources were separated by

5-10 degrees, one group of neurons became synchronized to one sound while

another population of neurons became synchronized to the second sound.

The talk " Independent Neural Populations Embody Perceptually Discrete

Auditory Streams " (#471) takes place Sunday, Feb. 7, at 4:15 p.m. PT in the

Disneyland Center and North Ballroom.

Moderate Hearing Loss at an Early Age Can Have Long-lasting Effects on the

Brain

Researchers have known for some time that severe hearing loss caused by

damage to the inner ear can alter the connections between nerve cells in the

auditory cortex, a part of the brain that processes sound. However, it was

not clear whether moderate forms of hearing loss caused similar changes to

the brain, and whether the neural connections remained altered as the brain

developed or they continued to mature until they reached a normal adult

state. In a new study from New York University, researchers asked if a

moderate form of hearing loss, similar to that caused by ear infections or

abnormalities in the middle ear, could alter the function of auditory cortex

connections and, if so, whether these changes persisted into adulthood. The

research team induced moderate hearing loss in young gerbils by removing one

of the middle ear bones from each ear. They then waited one week for some

animals to develop and allowed others to reach adulthood. When the

researchers examined the neural connections in the auditory cortex, they

found that those in the adult cortex were just as impaired after two

additional months of development as they had been shortly after the hearing

loss began. The researchers’ next step will be to learn what happens if the

animal’s hearing ability is returned after 2-3 weeks. They hope to find out

if a short period of moderate hearing loss early on — much like a childhood

ear infection — has a similar long-term effect on the function of neural

connections in the brain.

The poster " Conductive Hearing Loss Produces Changes in Cortical Inhibition

That Persist to Adulthood " (#814) takes place Monday, Feb. 8, at 1:00 p.m.

PT in the Disneyland Exhibit Hall.

Inner Ear Antiviral Holds Promise for Preventing Cytomegalovirus-related

Hearing Loss

Cytomegalovirus (CMV) is a widespread infection that is harmless for most

people. But if a mother passes it to her unborn child, serious health

problems can result, including hearing loss, and disorders of the brain,

bone marrow, liver, or spleen. Researchers estimate that up to 20 percent of

childhood hearing loss is caused by CMV infection. In other studies of

children with CMV, researchers had found that antivirals given intravenously

can improve hearing, though they can result in serious health complications.

Researchers at the University of Cincinnati and the Cincinnati Children’s

Hospital Medical Center are working to develop a safer, more effective way

to treat CMV-infected children with hearing loss by restricting the drug

treatment to the inner ear. They infected the inner ears of guinea pigs with

CMV and found the guinea pigs indeed had developed hearing loss. They then

delivered the antiviral drugs ganciclovir and cidofovir into the ear and

found that the virus had not only stopped replicating, but the guinea pigs’

hearing had improved. In addition to testing a liquid form of the antiviral,

the researchers are experimenting with a temperature-sensitive material that

changes from liquid to gel when subjected to body temperature. The gel could

be engineered to break down quickly and rapidly release the drug, or to

remain for a longer time for a sustained delivery of medication. In 2012,

the researchers plan to implement a clinical trial of CMV-infected children

with hearing loss to see if treating them with antiviral therapies in the

inner ear will help protect their hearing.

The poster " Intratympanic Delivery of Antivirals and the Effects on SNHL "

(#655) takes place Monday, Feb. 8, at 1:00 p.m. PT in the Disneyland Exhibit

Hall.

Growing an Ear Where No Ear Has Grown Before

Deep inside the inner ear, two types of nerve pathways shuttle their

messages to and from the brain. Afferent nerves carry messages from the ear

to the brain about the sounds your ear hears as well as balance information.

Efferent nerves carry information from the brain back to the inner ear to

help the ear make necessary adjustments. Researchers have known that the

efferent nerves in the inner ear are modified motor neurons that have

evolved from neurons that innervate muscles in the face. NIDCD-funded

researchers from the University of Iowa wanted to know if other motor

neurons in the body could be rerouted to innervate the ear if it were placed

in their way. Using tadpoles of an aquatic frog (Xenopus laevis), the

researchers transplanted the tadpole ears into the tadpole’s upper side

(trunk) or eye region and then watched what happened. They noticed that out

of 109 transplanted ears, 73 developed with necessary inner ear structures,

including sensory cells, called hair cells, which connect to the nerve

fibers. Using a dye that labels only motor neurons, they first found spinal

motor neurons had populated the ears in the tadpole’s trunk and cranial

motor neurons had populated the ears in the eye region. Next, using

antibodies, they demonstrated that connections were indeed forming between

the efferent nerves and the hair cells. Finally, using electron microscopy,

they showed that structures associated with afferent and efferent nerves

were both present in the transplanted ear. Because the afferent nerves

travel to the brain directly from the eye region or indirectly from the

trunk region by way of the spinal cord, the researchers now want to find out

what happens if the inner ear information travels to a non-auditory part of

the brain and how that information will be processed.

The poster " Transplantation of Xenopus Laevis Ears Reveals Ubiquitous

Rerouting of Motor Neurons to Become Efferents " (#552) takes place Monday,

Feb. 8, at 1:00 p.m. PT in the Disneyland Exhibit Hall.

NIDCD supports and conducts research and research training on the normal and

disordered processes of hearing, balance, smell, taste, voice, speech and

language and provides health information, based upon scientific discovery,

to the public. For more information about NIDCD programs, see the Web site

at www.nidcd.nih.gov.

The National Institutes of Health (NIH) — The Nation's Medical Research

Agency — includes 27 Institutes and Centers and is a component of the U.S.

Department of Health and Human Services. It is the primary federal agency

for conducting and supporting basic, clinical and translational medical

research, and it investigates the causes, treatments, and cures for both

common and rare diseases. For more information about NIH and its programs,

visit www.nih.gov.